linux.git/fs/netfs/main.c, branch for-next

Merge tag 'vfs-6.12.netfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2024-09-16T10:13:31+00:00

Pull netfs updates from Christian Brauner:
 "This contains the work to improve read/write performance for the new
  netfs library.

  The main performance enhancing changes are:

   - Define a structure, struct folio_queue, and a new iterator type,
     ITER_FOLIOQ, to hold a buffer as a replacement for ITER_XARRAY. See
     that patch for questions about naming and form.

     ITER_FOLIOQ is provided as a replacement for ITER_XARRAY. The
     problem with an xarray is that accessing it requires the use of a
     lock (typically the RCU read lock) - and this means that we can't
     supply iterate_and_advance() with a step function that might sleep
     (crypto for example) without having to drop the lock between pages.
     ITER_FOLIOQ is the iterator for a chain of folio_queue structs,
     where each folio_queue holds a small list of folios. A folio_queue
     struct is a simpler structure than xarray and is not subject to
     concurrent manipulation by the VM. folio_queue is used rather than
     a bvec[] as it can form lists of indefinite size, adding to one end
     and removing from the other on the fly.

   - Provide a copy_folio_from_iter() wrapper.

   - Make cifs RDMA support ITER_FOLIOQ.

   - Use folio queues in the write-side helpers instead of xarrays.

   - Add a function to reset the iterator in a subrequest.

   - Simplify the write-side helpers to use sheaves to skip gaps rather
     than trying to work out where gaps are.

   - In afs, make the read subrequests asynchronous, putting them into
     work items to allow the next patch to do progressive
     unlocking/reading.

   - Overhaul the read-side helpers to improve performance.

   - Fix the caching of a partial block at the end of a file.

   - Allow a store to be cancelled.

  Then some changes for cifs to make it use folio queues instead of
  xarrays for crypto bufferage:

   - Use raw iteration functions rather than manually coding iteration
     when hashing data.

   - Switch to using folio_queue for crypto buffers.

   - Remove the xarray bits.

  Make some adjustments to the /proc/fs/netfs/stats file such that:

   - All the netfs stats lines begin 'Netfs:' but change this to
     something a bit more useful.

   - Add a couple of stats counters to track the numbers of skips and
     waits on the per-inode writeback serialisation lock to make it
     easier to check for this as a source of performance loss.

  Miscellaneous work:

   - Ensure that the sb_writers lock is taken around
     vfs_{set,remove}xattr() in the cachefiles code.

   - Reduce the number of conditional branches in netfs_perform_write().

   - Move the CIFS_INO_MODIFIED_ATTR flag to the netfs_inode struct and
     remove cifs_post_modify().

   - Move the max_len/max_nr_segs members from netfs_io_subrequest to
     netfs_io_request as they're only needed for one subreq at a time.

   - Add an 'unknown' source value for tracing purposes.

   - Remove NETFS_COPY_TO_CACHE as it's no longer used.

   - Set the request work function up front at allocation time.

   - Use bh-disabling spinlocks for rreq->lock as cachefiles completion
     may be run from block-filesystem DIO completion in softirq context.

   - Remove fs/netfs/io.c"

* tag 'vfs-6.12.netfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (25 commits)
  docs: filesystems: corrected grammar of netfs page
  cifs: Don't support ITER_XARRAY
  cifs: Switch crypto buffer to use a folio_queue rather than an xarray
  cifs: Use iterate_and_advance*() routines directly for hashing
  netfs: Cancel dirty folios that have no storage destination
  cachefiles, netfs: Fix write to partial block at EOF
  netfs: Remove fs/netfs/io.c
  netfs: Speed up buffered reading
  afs: Make read subreqs async
  netfs: Simplify the writeback code
  netfs: Provide an iterator-reset function
  netfs: Use new folio_queue data type and iterator instead of xarray iter
  cifs: Provide the capability to extract from ITER_FOLIOQ to RDMA SGEs
  iov_iter: Provide copy_folio_from_iter()
  mm: Define struct folio_queue and ITER_FOLIOQ to handle a sequence of folios
  netfs: Use bh-disabling spinlocks for rreq->lock
  netfs: Set the request work function upon allocation
  netfs: Remove NETFS_COPY_TO_CACHE
  netfs: Reserve netfs_sreq_source 0 as unset/unknown
  netfs: Move max_len/max_nr_segs from netfs_io_subrequest to netfs_io_stream
  ...

netfs: Speed up buffered reading

2024-09-12T10:20:41+00:00

Improve the efficiency of buffered reads in a number of ways:

 (1) Overhaul the algorithm in general so that it's a lot more compact and
     split the read submission code between buffered and unbuffered
     versions.  The unbuffered version can be vastly simplified.

 (2) Read-result collection is handed off to a work queue rather than being
     done in the I/O thread.  Multiple subrequests can be processes
     simultaneously.

 (3) When a subrequest is collected, any folios it fully spans are
     collected and "spare" data on either side is donated to either the
     previous or the next subrequest in the sequence.

Notes:

 (*) Readahead expansion is massively slows down fio, presumably because it
     causes a load of extra allocations, both folio and xarray, up front
     before RPC requests can be transmitted.

 (*) RDMA with cifs does appear to work, both with SIW and RXE.

 (*) PG_private_2-based reading and copy-to-cache is split out into its own
     file and altered to use folio_queue.  Note that the copy to the cache
     now creates a new write transaction against the cache and adds the
     folios to be copied into it.  This allows it to use part of the
     writeback I/O code.

Signed-off-by: David Howells 
cc: Jeff Layton 
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/r/20240814203850.2240469-20-dhowells@redhat.com/ # v2
Signed-off-by: Christian Brauner

netfs: Remove NETFS_COPY_TO_CACHE

2024-09-05T09:00:42+00:00

Remove NETFS_COPY_TO_CACHE as it isn't used anymore.

Signed-off-by: David Howells 
cc: Jeff Layton 
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/r/20240814203850.2240469-10-dhowells@redhat.com/ # v2
Signed-off-by: Christian Brauner

netfs: Delete subtree of 'fs/netfs' when netfs module exits

2024-08-30T06:22:41+00:00

In netfs_init() or fscache_proc_init(), we create dentry under 'fs/netfs',
but in netfs_exit(), we only delete the proc entry of 'fs/netfs' without
deleting its subtree. This triggers the following WARNING:

==================================================================
remove_proc_entry: removing non-empty directory 'fs/netfs', leaking at least 'requests'
WARNING: CPU: 4 PID: 566 at fs/proc/generic.c:717 remove_proc_entry+0x160/0x1c0
Modules linked in: netfs(-)
CPU: 4 UID: 0 PID: 566 Comm: rmmod Not tainted 6.11.0-rc3 #860
RIP: 0010:remove_proc_entry+0x160/0x1c0
Call Trace:
 
 netfs_exit+0x12/0x620 [netfs]
 __do_sys_delete_module.isra.0+0x14c/0x2e0
 do_syscall_64+0x4b/0x110
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
==================================================================

Therefore use remove_proc_subtree() instead of remove_proc_entry() to
fix the above problem.

Fixes: 7eb5b3e3a0a5 ("netfs, fscache: Move /proc/fs/fscache to /proc/fs/netfs and put in a symlink")
Cc: stable@kernel.org
Signed-off-by: Baokun Li 
Link: https://lore.kernel.org/r/20240826113404.3214786-1-libaokun@huaweicloud.com
Acked-by: David Howells 
Signed-off-by: Christian Brauner

netfs: Revert "netfs: Switch debug logging to pr_debug()"

2024-07-24T08:15:37+00:00

Revert commit 163eae0fb0d4c610c59a8de38040f8e12f89fd43 to get back the
original operation of the debugging macros.

Signed-off-by: David Howells 
Link: https://lore.kernel.org/r/20240608151352.22860-2-ukleinek@kernel.org
Link: https://lore.kernel.org/r/1410685.1721333252@warthog.procyon.org.uk
cc: Uwe Kleine-König 
cc: Christian Brauner 
cc: Jeff Layton 
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner

netfs: Switch debug logging to pr_debug()

2024-06-12T12:25:41+00:00

Instead of inventing a custom way to conditionally enable debugging,
just make use of pr_debug(), which also has dynamic debugging facilities
and is more likely known to someone who hunts a problem in the netfs
code. Also drop the module parameter netfs_debug which didn't have any
effect without further source changes. (The variable netfs_debug was
only used in #ifdef blocks for cpp vars that don't exist; Note that
CONFIG_NETFS_DEBUG isn't settable via kconfig, a variable with that name
never existed in the mainline and is probably just taken over (and
renamed) from similar custom debug logging implementations.)

Signed-off-by: Uwe Kleine-König 
Link: https://lore.kernel.org/r/20240608151352.22860-2-ukleinek@kernel.org
Signed-off-by: Christian Brauner

netfs: Switch to using unsigned long long rather than loff_t

2024-05-01T17:07:35+00:00

Switch to using unsigned long long rather than loff_t in netfslib to avoid
problems with the sign flipping in the maths when we're dealing with the
byte at position 0x7fffffffffffffff.

Signed-off-by: David Howells 
Reviewed-by: Jeff Layton 
cc: Ilya Dryomov 
cc: Xiubo Li 
cc: netfs@lists.linux.dev
cc: ceph-devel@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org

netfs: Use mempools for allocating requests and subrequests

2024-05-01T17:07:35+00:00

Use mempools for allocating requests and subrequests in an effort to make
sure that allocation always succeeds so that when performing writeback we
can always make progress.

Signed-off-by: David Howells 
Reviewed-by: Jeff Layton 
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org

netfs: Remove ->launder_folio() support

2024-05-01T17:07:34+00:00

Remove support for ->launder_folio() from netfslib and expect filesystems
to use filemap_invalidate_inode() instead.  netfs_launder_folio() can then
be got rid of.

Signed-off-by: David Howells 
Reviewed-by: Jeff Layton 
cc: Eric Van Hensbergen 
cc: Latchesar Ionkov 
cc: Dominique Martinet 
cc: Christian Schoenebeck 
cc: David Howells 
cc: Marc Dionne 
cc: Steve French 
cc: Matthew Wilcox 
cc: linux-mm@kvack.org
cc: linux-fsdevel@vger.kernel.org
cc: netfs@lists.linux.dev
cc: v9fs@lists.linux.dev
cc: linux-afs@lists.infradead.org
cc: ceph-devel@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: devel@lists.orangefs.org

netfs: Replace PG_fscache by setting folio->private and marking dirty

2024-04-29T14:01:42+00:00

When dirty data is being written to the cache, setting/waiting on/clearing
the fscache flag is always done in tandem with setting/waiting on/clearing
the writeback flag.  The netfslib buffered write routines wait on and set
both flags and the write request cleanup clears both flags, so the fscache
flag is almost superfluous.

The reason it isn't superfluous is because the fscache flag is also used to
indicate that data just read from the server is being written to the cache.
The flag is used to prevent a race involving overlapping direct-I/O writes
to the cache.

Change this to indicate that a page is in need of being copied to the cache
by placing a magic value in folio->private and marking the folios dirty.
Then when the writeback code sees a folio marked in this way, it only
writes it to the cache and not to the server.

If a folio that has this magic value set is modified, the value is just
replaced and the folio will then be uplodaded too.

With this, PG_fscache is no longer required by the netfslib core, 9p and
afs.

Ceph and nfs, however, still need to use the old PG_fscache-based tracking.
To deal with this, a flag, NETFS_ICTX_USE_PGPRIV2, now has to be set on the
flags in the netfs_inode struct for those filesystems.  This reenables the
use of PG_fscache in that inode.  9p and afs use the netfslib write helpers
so get switched over; cifs, for the moment, does page-by-page manual access
to the cache, so doesn't use PG_fscache and is unaffected.

Signed-off-by: David Howells 
Reviewed-by: Jeff Layton 
cc: Matthew Wilcox (Oracle) 
cc: Eric Van Hensbergen 
cc: Latchesar Ionkov 
cc: Dominique Martinet 
cc: Christian Schoenebeck 
cc: Marc Dionne 
cc: Ilya Dryomov 
cc: Xiubo Li 
cc: Steve French 
cc: Paulo Alcantara 
cc: Ronnie Sahlberg 
cc: Shyam Prasad N 
cc: Tom Talpey 
cc: Bharath SM 
cc: Trond Myklebust 
cc: Anna Schumaker 
cc: netfs@lists.linux.dev
cc: v9fs@lists.linux.dev
cc: linux-afs@lists.infradead.org
cc: ceph-devel@vger.kernel.org
cc: linux-cifs@vger.kernel.org
cc: linux-nfs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org